I am proposing a training program with didactic coursework and experiments that are logical extensions of our previous work in understanding how Nf1 functions in cardiovascular development. Neuro-fibromatosis type 1 (Von Recklinghausen's Disease) is an autosomal dominant condition affecting 1 in 3000-4000 individuals. It is characterized by pathology of neural crest-derived tissues, but also causes cardiovascular abnormalities. The gene NF1 encodes neurofibromin, a large molecule that in part acts as a ras GTPase activating protein (GAP). Mice homozygous for a null allele of the murine homologue (Nf1) have a set of embryonic lethal cardiovascular defects reminiscent of common forms of congenital heart disease. Endothelial specific disruption of Nf1 reproduces much of this cardiovascular phenotype. Further, we believe that it occurs through the ras-GAP function of neurofibromin and its effect on nuclear localization of the transcription factor NFATc1 (nuclear factor of activated T-cells). Specific Aim 1 will test the hypothesis that ras-GAP function is the critical aspect of neurofibromin responsible for proper cardiovascular development. The ras GAP related domain of neurofibromin has been knocked into the Rosa26 locus by me and will be expressed in a tissue-specific manner in mice through the activity of cre recombinase. Specific Aim 2 will test the hypothesis that the loss of Nf1 in vascular smooth muscle will recapitulate the vascular disease of neurofibromatosis. I will test this by crossing floxed Nf1 mice with a tamoxifen-inducible, smooth muscle specific cre line. Specific Aim 3 will test the hypothesis that NF1 and NFATc1 are in the same genetic pathway in cardiovascular development. Through genetic analysis of mice and mouse embryos deficient in both NF1 and NFATc1, I will determine the role of NFATc1 in the development of the cardiovascular phenotype of Nf1 null embryos. Finally, Specific Aim 4 will extend our previous work on the observation that NFATc1 undergoes nuclear localization in endothelial cells in the setting of elevated ras activity. I will continue testing specific signaling pathways downstream of ras to determine those that are critical for this phenotype. This experimental work will be supported by a foundation of didactic training in molecular and developmental biology. Together this training program will prepare me for independent investigation, lead to a better understanding of cardiovascular abnormalities in neurofibromatosis, and address fundamental issues of cardiovascular development.